The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The speed at which a rotating data storage device, such as a magnetic or an optical storage device, executes read and write operations affects the performance of a computer or other host device. A rotating data storage device may be, for example, a hard disk drive (HDD), a compact disc (CD) drive, a digital versatile disc (DVD) drive or a high definition/high data storage disc drive. Operational delay in the rotating data storage device can cause a corresponding delay in operation of the host device.
Typically, a HDD includes one or more magnetic disks. Each disk includes tracks that store data. The tracks are divided into sectors. A read/write head is used to read from or write to the sectors. The sectors are accessed serially beginning with a target start sector. An index pulse identifies the first sector of a track of a disk and a sector pulse identifies the start of a sector. In use, the HDD receives a command signal that identifies a target sector or a block of target sectors for a read/write operation. The HDD rotates the disk to the first target sector in the block of target sectors before proceeding with the read/write operation.
The read/write operation has associated delays. A delay occurs when the read/write head is not over a sector that is adjacent to and precedes the target start sector at the moment when the HDD is ready to perform the read/write operation. The delay is equal to the wait time for the disk to rotate to the target start sector. In certain instances, this delay can approach the amount of time required for one revolution of the disk.
The HDD performs preparation tasks prior to performing a read/write operation. These preparation tasks include determining the current sector that the read/write head is over. The rotating medium continues to rotate during the preparation tasks. As such, the disk may rotate past the target start sector before the HDD is ready to perform the read/write operation. For this reason, the associated delay can be longer than one revolution of the disk.